Saturday, August 22, 2015

Mu-metal Part 2

In Part 1 of this 3-part series, I found a new friend: mu-metal. It worked wonders in my line conditioner so I thought I might give it a go in my low-level equipment.

I tried the same cabinet-coating approach I did with the line conditioner in my OPPO BDP-105. I took off the rubber feet, cut out a piece to fit on the bottom, used carpet tape to hold it in place, and then put the feet back on through x-shaped holes I made with an XACTO knife. I also cut a vent hole under the power supply to allow airflow for proper cooling.

I pulled off the cover and coated the three interior surfaces in a similar way (carpet tape & cooling hole).

Note that the holes are much smaller than the originals but the unit does not get any hotter than it did before.

Put it back together and you have a pretty well shielded chassis without a lot of work.

So the surprise is in the sound. This unit has a nicely isolated toroid power transformer so I did not wrap this transformer. But the results were almost as amazing as with the line conditioner in Part 1. The noise floor drops and inner details come alive. If you have ever listened to a preamp with an outboard power supply, this mod has a similar effect. You just won't believe your ears (sort of like hearing a high-quality paper-in-oil capacitor for the first time - you just never forget it).

Mumetal is a thing of beauty and it is not that expensive. The trick is to cut it with a scissors and not a saw or shears. Wrap it in circles or bend it once (rebending, while possible, is not really a good option). It does leave VERY sharp edges so you also must be careful not to get a steroid-sized paper cuts when handling this stuff. Just be careful and try this yourself. Wrap those power transformers and box up those low-level signal components and be prepared for a shock.
So if my power conditioner and OPPO BDP-105 responded, what about my preamp? See part 3 to find out.

Yours for higher fidelity,

Philip Rastocny

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